Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Sep. 30, 2015
Income Tax Disclosure [Abstract]
Effective income tax rate	30.40%	34.70%	27.20%	28.90%
Unrecognized tax benefits, uncertain tax positions	$ 6.2		$ 6.2		$ 4.6
Unrecognized tax benefits, accrued interest	$ 0.3		$ 0.3		$ 0.2